Analysis and Correction of Gradient Nonlinearity Bias in Apparent Diffusion Coefficient Measurements
Analysis and Correction of Gradient Nonlinearity Bias in Apparent Diffusion Coefficient Measurements
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DOI：
10.1002/mrm.24773
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发表时间：
2014-03-01
影响因子：
3.3
通讯作者：
Chenevert, Thomas L.
中科院分区：
文献类型：
--
作者：
Malyarenko, Dariya I.;Ross, Brian D.;Chenevert, Thomas L.
MRI系统的梯度非线性导致空间依赖性b值，从而导致临床相关视野内表观扩散系数（ADC）测量的高非均匀性误差（10-20%）。这项工作寻求实际的校正程序，有效地减少观察到的ADC偏差介质中的任意各向异性在最少measurements.MethodsAll-inclusive偏差分析认为扩散和成像梯度的空间和时域交叉项。所提出的校正是基于梯度非线性张量旋转到扩散梯度框架中，其中b矩阵的空间偏差可以由其欧几里德范数近似。修正效率的建议的程序进行数值评估的范围内的模型扩散张量各向异性和orientations.ResultsSpatial依赖的非线性校正项占大部分（75-95%）的ADC偏置FA=0.3-0.9。对于各向异性扩散，残余ADC非均匀性误差被放大。这种近似消除了对全扩散张量测量和对角化以导出校正的ADC的需要。在临床MRI systems.ConclusionsThe建议的简化的校正算法出现足以控制ADC的非均匀性误差在临床研究中使用三个正交扩散测量的实际情况进行了概述。各向异性介质的ADC偏置的最有效降低是通过非实验室扩散梯度实现的。Magn Reson Med 71：1312-1323，2014。(c)2013 Wiley Periodicals，Inc.
PurposeGradient nonlinearity of MRI systems leads to spatially dependent b-values and consequently high non-uniformity errors (10-20%) in apparent diffusion coefficient (ADC) measurements over clinically relevant field-of-views. This work seeks practical correction procedure that effectively reduces observed ADC bias for media of arbitrary anisotropy in the fewest measurements.MethodsAll-inclusive bias analysis considers spatial and time-domain cross-terms for diffusion and imaging gradients. The proposed correction is based on rotation of the gradient nonlinearity tensor into the diffusion gradient frame where spatial bias of b-matrix can be approximated by its Euclidean norm. Correction efficiency of the proposed procedure is numerically evaluated for a range of model diffusion tensor anisotropies and orientations.ResultsSpatial dependence of nonlinearity correction terms accounts for the bulk (75-95%) of ADC bias for FA=0.3-0.9. Residual ADC non-uniformity errors are amplified for anisotropic diffusion. This approximation obviates need for full diffusion tensor measurement and diagonalization to derive a corrected ADC. Practical scenarios are outlined for implementation of the correction on clinical MRI systems.ConclusionsThe proposed simplified correction algorithm appears sufficient to control ADC non-uniformity errors in clinical studies using three orthogonal diffusion measurements. The most efficient reduction of ADC bias for anisotropic medium is achieved with non-lab-based diffusion gradients. Magn Reson Med 71:1312-1323, 2014. (c) 2013 Wiley Periodicals, Inc.